The exhaust is not that loud unless wide open throttle and from the interior its subdued. BMW puts a little valve control on the exhaust to close off one of the pipes unless you hit wide open throttle. At start-up however both pipes are open for emission control reasons. This is regardless of the model.

Some people prefer a little noise than whisper quiet. This one sounds like what I hear every morning:

I thought it was the opposite. I thought the valve was closed during startup to allow the cats to heat up faster.